In Computer Science, a TBox is a "terminological component"—a conceptualization associated with a set of facts, known as an ABox.[1]

The terms ABox and TBox are used to describe two different types of statements in ontologies. TBox statements describe a conceptualization, a set of concepts and properties for these concepts. ABox are TBox-compliant statements about individuals belonging to those concepts. For instance, a specific tree is an individual for the concept of "Tree", while it can be stated that trees as a concept are material beings that have to be positioned on some location it is possible to state the specific location that a tree takes at some specific time.

Together ABox and TBox statements make up a knowledge base. A TBox is a set of definitions and specializations.

A definition is an equality with an atomic concept on the left hand, for example: a bachelor is a student who is undergraduate.

A specialization is an inclusion with an atomic concept on the left hand, for example: the set of students is a subset of the people who are studying.